1. Field of the Invention
The present invention relates to a print control method, apparatus, and a storage medium. Particularly, the invention relates to a print control apparatus for generating print image data of a particular color space representing a print object document in the form of a plurality of color components into which the document has been separated by performing predetermined processing of document information of the print object document, in order to print the document with a printer using coloring agents of the plurality of color components. Further, the invention relates to a print control method which is applicable to the print control apparatus, and a storage medium storing a print control program for causing a computer to function as the print control apparatus.
2. Description of the Related Art
Recently, as the performance of copying machines and printers has been improving, cases in which reproductions of bank bills, marketable securities, or the like copied by copying machines or printers are illegally used are increasing. In order to prevent the illegal use of the reproductions, it is particularly desired that a technology be secured which can determine the authenticity of various documents (in addition to bank bills or marketable securities, for example, passports, various title certificates, residence certificates, birth certificates, insurance papers, guarantee certificates, and confidential documents) printed on various kinds of paper with high accuracy.
It is known to provide a technology for composing, on various paper printed documents, an image which allows identification of the authenticity of the documents by utilizing the fact that only K ink contains an infrared absorption color of all the inks for color components of Y (Yellow), M (Magenta), C (Cyan), and K (Black). First regions formed in m by m pixels (m is an integer not lower than 2) and second regions formed in n by n pixels (n is an integer not lower than 1 and lower than m) are provided in an identification image. Plural independent first regions are arranged around a single second region with no spaces between, and plural independent second regions are arranged along the outer periphery of a single first region at substantially equal intervals. An embedded image, to be printed with the inks of Y, M, and C is placed on the first regions in the form of a dot image, and an embedding image to be printed with the K ink is placed on the second regions in the form of a dot image.
According to the above described technology, in an authorized print method, the embedding image embedded in an identification image is printed only with the K ink containing the infrared absorption color, so that existence of the embedding image can be recognized when the identification image is observed under irradiation of infrared light. On the other hand, when a document with an identification image printed with an authorized print method is copied (for example, by reading the document with the identification image with a scanner and printing it with a printer), the scanner cannot distinguish “black” in the embedded image formed with the inks of Y, M, and C, from “black” in the embedding image formed with the K ink. Therefore the embedded image and the embedding image cannot be separated from each other. Accordingly, it is possible to determine that the copied document is a fake because the embedding image cannot be reproduced in the identification image of the copied document (i.e., the existence of the embedding image cannot be recognized even if the identification image is irradiated with infrared light). Thus, in this technology special inks are not required, and determination of the authenticity of a document can be realized at low cost.
The above described technology is based on printing with the inks of Y, M, C, K commonly used in commercial printing. Also for toners of Y, M, C, K, since only K toner contains the infrared absorption color in the same manner as the inks, it is expected that determination of the authenticity of a document will be realizable by applying the technology in a case where a document is printed with a printer which forms images electrophotographically using the toners of Y, M, C, K.
However, when a document is printed with a printer on the basis of information of a print object document, although the printing is finally performed using the toners of Y, M, C, K, in order to effectively utilize resources such as processing speed and memory, usually the information of the print object document is once converted into image data of a color space other than Y, M, C, K such as R, G, B or L*a*b at some midpoint to perform various kinds of image processing. Then the image data of the color space other than Y, M, C, K is reconverted into the image data of Y, M, C, K to perform printing. Once the document information to which the information of the identification image is added is converted into the image data of the color space other than Y, M, C, K, the information of the embedding image and the information of the embedded image, both included in the identification image, are mixed together in the post-conversion image data. Therefore, there are problems in which an identification image represented by the original identification image cannot be correctly printed and the authenticity of the document cannot be determined on the basis of the printed identification image.